In this field there are known several methods of clamping a generally cylindrical shank into the clamping portion of a cutting tool. One method makes use of a conical collet and a sleeve, thread rotated around the collet to reduce its diameter, thereby clamping the shank of the cutting insert. This clamping method has a disadvantage in that after the cutting insert is replaced, it is difficult to position the new cutting insert in the exact original orientation of the old cutting insert. Repeatability of the orientation of a cutting insert is a very important feature when it comes to machining, for example, small internal bores. The slightest deviation in the orientation or position of the shank end is magnified at the cutting portion end, most likely resulting in a faulty surface finish.
In EP 0385280 an internal turning chisel is described to have a hook-ended tool, clampable into a recess located in the chuck portion of the chisel. In this clamping method, a clamp screw is threaded into the chuck, pressing against the shank portion of the hook-ended tool which is located within the recess. Consequently, the shank portion is pressed against the other side of the chuck, with respect to the clamp screw. Although this method is better than the collet method in terms of repeatability, it has certain disadvantages. For one, the clamp screw applies force to a single point at one end of the hook-ended tool. Therefore, the force is applied asymmetrically with respect to the tool's longitudinal axis. Another aspect of this method is that, as with most types of screws, there is a limit to the amount of torque the screw can sustain and consequently apply on the shank. Therefore, without using a special torque-limiting tool, plastic deformation may develop in the threads of either the screw or the screw bore. This may prove to be problematic in terms of repeatability. There is yet another aspect which pertains to most clamping methods which require the use of screws. The process of turning a screw is time consuming and for the most part, there is a need for a torque applying tool (e.g. a screwdriver). For example: positioning the screwdriver over the screw head, turning the screwdriver in one direction, replacing the tool and then turning the screw in the other direction.